Z Axis HIPS compressing?

I’m still pretty new to 3D Printing, and I’ve been doing some decent prints using HIPS.
I’ve started noticing something in some of my prints, where it seems either the print head or the material is compressing or collapsing. I’ve attached two images from my latest print.
You’ll see there is a good portion of the lower part of the print where there is plastic that seems to be bulging out. It seems to resolve itself later on, after a certain height.
The print was made with standard HIPS settings in Cura.
As a side note, I’ve also noticed when I tried PLA with this print, it seems like the head was grinding over the surface of the print when it moved over the body of it to the other side.


It could just be an artifact of removing the part from the bed, but it looks to me like you had a bit of lifting off of the bed in the center. That, coupled with a possibly incorrect filliament diameter setting inside of CURA (measure the exact diameter with calipers, update it from the default 2.85 or 3.00 to match) may be leading to overextrusion. Try backing the infil down from 100% at first if you have it up that high, adjust the filliament, and if that doesn’t do the trick, potentially calibrate your extruder esteps.

Thanks for the quick reply Piercet, I’ll check my settings again when I’m home. If I need to calibrate the esteps, how do I do that on the mini?

It should be pretty close out of the box unless you flashed the firmware and forgot to enter the correct esteps value, but here’s a guide on how to do it yourself. http://www.instructables.com/id/How-to-calibrate-the-Extruder-on-your-3d-Printer/

Thanks, hopefully I won’t need to play with that, but it’s good to know.

I was having that exact problem, looked like a “shrinkage” of the first few layers then a bulging of the next few layers, when printing with HIPS and the default CURA profiles. I lowered the bed temp from 110C to 100C, and the problem 99% disappeared. Running at 100C didn’t affect adhesion. Not sure if my bed is just running 10C hotter than commanded, or if 110C is just too hot for HIPS.

Anyway, try changing bed temp to 100C and see if it improves the issue. It did for me!

Thanks everyone for the suggestions.
It looks like between changing the flow rate, bed temperature and the filament diameter settings I’m getting much better and accurate prints now.

I adjusted the following:
Bed Temp: 100 (default 110)
Flow Rate: 90% (default 100%)
Filament Diameter: 2.95 (default 2.85)

I’ve attached an image of the results (I found a funny Orcarina like instrument on Thingiverse). The one on the right is using default HIPS settings, you can see it’s a little shorter, and there is bulging build-up at the bottom curve.
The one on the left is with the new settings, and it’s much better.